In a long term evolution (LTE) system, Multimedia Broadcast Multicast Service (MBMS) data may be transmitted in MBMS Single Frequency Network (MBSFN) mode. That is, multiple evolved NodeBs (eNBs) transmit radio signals carrying the same MBMS data with the same frequency at the same time from multiple cells. An area covered by the multiple eNBs that transmit the MBMS data in MBSFN mode is called an MBSFN area. User equipments (UEs) in the MBSFN area may consider that only one transmitter is transmitting radio signals and receive the MBMS data.
Data transmitted by the eNBs in the MBSFN area is the same, and the physical resources used are the same. That is, information of each eNB is synchronous. For example, a synchronization (SYNC) entity is set on the broadcast multicast-service center (BM-SC) side on the core network (CN) and an SYNC entity is set on the eNB side. The SYNC entity on the BS-SC side sets a time stamp for various MBMS data packets and provides the time stamp for all eNBs in the MBSFN area. Specifically, the BM-SC may include multiple MBMS data packets in a synchronization sequence. The SYNC entity on the BM-SC side sets the same time stamp for MBMS data packets in a synchronization sequence and transmits a type 0 control packet (namely, a type 0 Protocol Data Unit (PDU), hereinafter referred to as a type 0 PDU) after the BM-SC transmits the synchronization sequence. The type 0 PDU is used to notify the eNBs of transmission completion of the current synchronization sequence. To improve the reliability, the SYNC entity on the BM-SC side transmits a type 0 PDU group but not merely a type 0 PDU. The type 0 PDU group includes all type 0 PDUs that include the same information and are transmitted repeatedly. For example, after a synchronization sequence is transmitted, a type 0 PDU is transmitted consecutive three times. The three type 0 PDUs form one type 0 PDU group.
When receiving the MBMS data, eNB determines the time when the BM-SC starts to transmit the synchronization sequence according to the time stamp obtained by the SYNC entity on the eNB side, and determines reception completion of the synchronization sequence according to the type 0 PDU. The eNB transmits the received MBMS data packets according to the time stamp of the received MBMS data packets.
If the eNBs in the MBSFN area have buffered all MBMS data packets to be transmitted in a Dynamic Schedule Period (DSP) before the DSP, the eNBs can generate the same Dynamic Schedule Information (DSI) to implement the same dynamic scheduling for the same MBMS data packets. For example, the eNBs have buffered all the MBMS data packets to be transmitted in the DSP before the DSP. The eNBs determine the time for transmitting the MBMS data packets, and then generate DSI corresponding to the DSP to indicate scheduling of the DSP, for example, the start positions of data packets of different services in the DSP. In a first MBSFN subframe on a multicast channel (MCH), the eNBs transmit the DSI of the corresponding transmission channel in the DSP and transmit the data packets according to the scheduling result. A UE at the receiving end receives the DSI, knows eNB scheduling according to the DSI, and thus selects the time when the eNBs transmit data that is interesting to the UE to receive data.
In evolved MBMS, air interface resources of the MBSFN service are reserved in advance in a manner of semi-persistent scheduling. A reserved subframe that is used to transmit MBSN data is called an MBSFN subframe. To meet different quality of service (QoS) requirements of different MBSFN services, the evolved MBMS maps the MBSFN services to different MCHs, and the different MCHs adopt different Modulation Coding Schemes (MCSs) to achieve different QoS. Different MCHs do not share a reserved MBSFN subframe. To reduce scheduling overheads, the eNBs perform air-interface transmission scheduling for MBMS data in each DSP. The eNBs only schedule MBSFN data of which time stamp is earlier than the start time of the corresponding DSP. Generally, the eNBs schedule the corresponding MBSFN data in one DSP that is later than a time stamp.
In the prior art, transmission between a BS-SC and an eNB is based on the Internet Protocol (IP), which may cause loss of MBMS data packets or a type 0 PDU. If an eNB in an MBSFN area cannot normally receive at least two consecutive MBMS data packets in a synchronization sequence or all type 0 PDUs that indicate transmission completion of a synchronization sequence, the eNB generates incorrect DSI, which may interfere with other eNBs and cause incorrect data receiving of the UE.